Energy efficiency leads not only to cost saving, but more importantly to reduced CO2 emission. This article explains how the increased energy efficiency is implemented in feed mills.
As a result of the energy saving practices carried out in one of Europe's leading animal feed producers with a total annual production capacity of 550 thousand tons at its four facilities, the average electrical energy need has been reduced by 4% in the last ten years, while the thermal energy consumption has been reduced by 10 kWh/t. Here, both the improvements achieved on the basis of the facility and the ongoing applications will be mentioned.
First Plant
This facility, which is about 20 years old and has produced a total of 6 million tons of feed until today, was built with as high energy efficient mill at the first installation. In the plant, which prefers a multi-stage grinding system instead of direct grinding, the direct energy requirements are reduced by approximately 30% by using a double-pass crusher mill and hammer mills. Achievements so far:
Ongoing / Planned Application(s):
Second Plant
This facility was rebuilt about 15 years ago and a total of 1.5 million tons of feed has been produced since the renovation. In the post-grinding system, there is a pre-screening stage before the hammer mills. This combination reduces the energy requirement by approximately 20% compared to the conventional grinding system. Frequency converters allow the grinding quality of the feed to be adjusted during production and significantly reduce the starting current. The exhaust heat of the compressed-air generators and the flash steam of the condensate separation system of the steam boilers are used for preheating the feed water in the facility. A significant reduction in annual natural gas consumption has been achieved by this measure.
Application of differential-pressure controllers on the large dust collection filters, which slashes the purge-air requirement, is planned in the plant. The payback time of this investment is also very quick.
Third Plant
This facility, which was established 30 years ago and increased its capacity 12 years ago, has produced over 1.5 million tons of feed since the first day. The followings have been achieved with the energy saving measures taken during the renovation:
Additionally, installation of a multistage grinding system using two-pass crushing mills and hammer mills is planned. This will reduce the energy requirement by 30% in comparison to a direct-grinding system. The grinding quality can be automatically controlled by the process control system.
Fourth Plant
This facility, on the other hand, is 55 years old, and various innovations such as capacity increase and transition to full automation were made 15 years ago. The total amount of feed produced is over 2.5 million tons since the first day.
An automation scenario has been written for the plant in such a way that the mixing line and the pellet press and the expander line will produce feed fully automatically during the night shift. In case of failure, the plant's control system switches to safe mode. In addition, facility and personnel safety must be ensured at all times. The new system can warn personnel in case of an accident; remote maintenance is also possible. In unmanned operation, the control system should make the decisions made by the experienced operator. For example, sensors monitor temperatures and vibrations in the hammer mill, mixer, expander as well as machine bearings.
Energy savings were achieved with the installation of a multi-stage grinding system using pre-screening and intermediate screening and tow-pass crushing mills in front of the hammer mill at the facility. This reduces the energy requirement by approximately 30% compared to a direct grinding system. The grinding quality can also be controlled automatically.
Energy Saving Continues
Energy saving optimization is still an active subject for feed mills. For example; over the past ten years, about 5% electrical energy and 17% thermal energy per metric ton of feed produced have been conserved – while the rate of thermally hygienised feed to total products was increased from 60% to 100%.
Efficient Energy Utilization
Combustion of chemically stored energy to produce electrical energy increases the calorific value of heating oil approximately three times compared to pure steam production. This process, called "combined heat and power generation", significantly increases the "exergetic" efficiency, which can be converted to another form of energy without loss. This means that almost all of the chemical potential found in the fuel (heating oil, natural gas) is used, as electrical energy is generated as well as heat.
Exhaust heat of compressors
The heat dissipated by the air compressors is systematically used to preheat the boiler feed water instead of being blown into the atmosphere, or to operate the hot air exchangers instead of steam. With the use of exhaust heat alone, together with other heat recovery measures, a remarkable amount of thermal energy saving has been achieved.
CO2 Label
In facilities with a comprehensive energy management system, CO2 emission to the atmosphere is approximately 500 metric tons less per year, while feed volume can increase by 10%. In this way, in a 10-year period, approximately 3,100 tons less CO2 can be released in total in environmentally friendly and nature-sensitive facilities.
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